The proliferation of extended capability medical monitoring instrumentation has tended, among other things, to increase the risk that a patient may be subjected to spurious or untoward electrical effects through the patient-monitoring device interface. Unless such possibilities are accounted for, there is a risk, at the minimum, that the data representing patient parameters being monitored will be subjected to interference, cross talk, or the like, and thus be rendered misleading as meaningless; at the maximum, that the patient actually is exposed to a risk of hazard. These risks are avoided by providing effective patient-utilization apparatus isolation units, whereby monitoring signals and the like from the patient are effectively and certainly delivered to the monitoring apparatus or the like utilization device, free of the abovementioned risks.
Numerous single channel and multiple signal isolated interference devices are commercially available, including those which use magnetic and optical coupling techniques.
Especially for patient monitoring applications, but no doubt generally in applications employing low signal levels but requiring a high degree of isolation security, optical coupling approaches are generally found wanting.
Typically, these approaches require too much isolated side power to operate the light sources, typically light emitting diodes; poor dynamic range or linearity; lack of ability readily to inspect isolation integrity; and all nevertheless require at least one transformer to pass power to the isolation side circuits.
Since a magnetic coupling will generally be required for purposes of conveyance of power, then, it is an object of the present invention to provide isolation interface circuits which utilize the magnetic coupling approach for patient to utilization apparatus signal channels as well, thereby obviating the need for any optical coupling, and the consequent drawbacks above specified.
It is a further object of the present invention to provide an approach to isolation interfacing wherein the magnetic coupling circuits are of moderate size, weight, and cost, are generally uniformly configured for power and for signal channel applications, and which provide isolation at quite high frequencies, perhaps in the range near 1 megahertz.
Yet another object of the present invention is to provide isolation interface circuits wherein the physical isolation is visually apparent to the user, thereby allowing the fact of the interface to be readily apparent to the user, and providing the physical, electrical, and psychological security inherent to such arrangements.